For example, a gas water heater is generally configured to use a fin-and-tube type heat exchanger to recover heat from combustion gas generated by a gas burner for heating water for hot water supply.
If such a gas water heater is configured as a commercial-use water heater, for example, that is used in restaurants and the like and having a relatively high hot-water supply capability (size number) unlike a home-use water heater, a large-scale gas burner covering a large gas combustion area is used. Accordingly, the heat exchanger to be used needs to be of large size in accordance with this gas combustion area. Thus, each plate fin is actually sized to have a considerably increased length in the right-and-left width direction that is approximately equal to the width of the gas combustion area of the gas burner.
Also in the conventional instance, there has been a water heater having a configuration different from that of the above-described water heater. This water heater is configured such that two heat exchangers are stacked vertically in two stages and connected to each other through their heat transfer tubes (for example, see Japanese Patent Laying-Open No. 10-19377).
Furthermore, as another example of the conventional heat exchanger, there has also been a heat exchanger in a 2-circuits-in-1-case system in which two plate fin blocks are arranged in one case (for example, see Japanese Patent Laying-Open No. 2001-91057).